1. Field of the Invention
This invention lies in the field of electronic switching means. More particularly, it concerns the control of solid state conduction devices for switching inductive loads into and out of A.C. power circuits.
2. Description of the Prior Art
In the prior art there are a number of examples of circuits which have been proposed over recent years for controlling the electronic switching of A.C. power through inductive loads. Many of these have been unworkable. Others have many disadvantages. For instance, a large proportion of them are very complicated and use bridges in order to determine the proper starting times, etc. Others utilize capacitors, of varying sizes, to adjust the power factor of the load to be substantially resistive. The problem, however, is to know precisely what magnitude of capacitance to use.
In many of these circuits, because of the unsynchronized operation of the thyristor type triac switches, the circuits often provide large transient spikes of voltage or current in the circuits, at the switching times.